1. Field of the Invention
This invention pertains generally to skin tone detection systems and methods, and more particularly to skin tone detection systems and methods for digital video images in YCbCr space.
2. Description of Related Art
In order to minimize bandwidth for transmission and the amount of storage space in video applications, compression techniques are utilized to reduce the size of the video. These compression techniques generally have an adverse effect on the quality of the video image, such as texture loss and other artifacts.
Because facial regions receive a high degree of attention as opposed to other objects in the image, one way for increasing the quality of the image is to concentrate processing procedures on face regions.
There are various known approaches for detecting face regions in images. These include feature-based, motion-based and color-based approaches. Feature-based approaches try to identify a face region by detecting certain facial features, such as the eyes, the nose and the mouth. Motion-based approaches operate on the principle that a moving region in an image is likely to be a face. A color-based approach looks for skin-colored regions in an image.
Many of the known face detection approaches are computationally expensive, and are thus not ideal for real time applications such as digital video coding. The preferred approach for such applications is a color-based approach.
Color-based, or skin tone face detection involves extracting the regions of an image which have color corresponding to skin color. The skin tone detection system should be able to detect a range of skin tones, such as African, Asian and European, and should also be able to detect skin color irrespective of the lighting conditions under which the image is captured.
Accordingly, many known color-based face detection methods involve complex parametric modeling of the human skin tone. Such modeling requires a heavy computation cost, and while such computation costs may be acceptable in still image editing of JPEG or other still image files, they are prohibitive in current video standards (e.g., MPEG or H.263).
Accordingly, it is an object of the present invention to provide an improved skin tone detection algorithm for video images.
It is a further object of the present invention to provide a skin tone detection algorithm that has minimal computational costs and that improves the visual quality of video images by identifying human skin tone regions for further processing by a video encoder.